¹¹⁹Sn solid-state NMR as a local probe for correlations in CeRu₄ Sn₆

CeRu₄ Sn₆ is a tetragonal ternary compound which develops strong correlations at low temperatures. NMR investigations on the multiscripts(Sn ( I = frac(1, 2) ), mml:none(), mml:none(), prescripts(), mml:none(), 119) nuclei are reported for the first time. The Knight shift multiscripts(K ( T ), mml:none(), mml:none(), prescripts(), mml:none(), 119) at magnetic fields of about 1.8 T is relatively small ( ∼ - 0.33 %) and no significant temperature dependence could be resolved. The behavior of the spin-lattice relaxation rate multiscripts(( 1 / T₁ ), mml:none(), mml:none(), prescripts(), mml:none(), 119) at temperatures above approximately 20 K is consistent with a small gap semiconductor ( 1 / T₁ ∼ T exp ( - Δ / k_B T ), Δ / k_B = 33 K). At lower temperatures multiscripts(( 1 / T₁ ), mml:none(), mml:none(), prescripts(), mml:none(), 119) shows an increase towards weaker T-dependence. This is interpreted as the formation of strong correlations around T^* = 10 K and is consistent with specific heat results in the framework of the Korringa model. Furthermore, measurements on the isostructural reference compound LaRu₄ Sn₆ are presented.